1. Field of the Invention
This invention relates to an arrangement for detecting a film cartridge being loaded into a cartridge chamber.
2. Description of Related Art
With regard to a film cartridge of a so-called thrust type having no leader part of film left outside of the film cartridge, an arrangement for detecting the position of the film cartridge relative to a cartridge chamber of a camera in automatically loading and ejecting the film cartridge into and from the cartridge chamber has been proposed in Japanese Patent Application No. HEI 7-135451.
According to the proposed arrangement, in automatically loading and ejecting the film cartridge into and from the camera, three positions, or states, of the film cartridge relative to the cartridge chamber must be detected in order to minimize the possibility of malfunctions of related mechanisms. The three positions or states are as follows.
(1) a position where the film cartridge has become loadable by an automatic loading mechanism (start of drawing-in), PA1 (2) a state in which the film cartridge has been completely loaded into the cartridge chamber by the automatic loading mechanism (completion of loading), and PA1 (3) a state in which the film cartridge has been ejected from the cartridge-chamber by an automatic ejecting mechanism and, then, the film cartridge has been completely pulled out by an operator (pulling-out).
In the case of Japanese Patent Application No. HEI 7-135451, two switches are used in combination as a means for detecting the three positions or states.
FIG. 10 shows the arrangement of a cartridge chamber proposed in the above Japanese Patent Application No. HEI 7-135451. In this arrangement, automatic loading and ejecting mechanisms are arranged to automatically load and eject a film cartridge 101, which is shown in FIG. 11, from the lower side of the camera by engaging with a recessed part 101-a of the film cartridge 101.
Referring to FIGS. 10 and 11, an engaging claw 104 which is urged to rotate by a spring 103 is pivotally supported for rotation by an ascending/descending member 102 and is arranged to engage with the recessed part 101-a of the film cartridge 101. The ascending/descending member 102 is arranged to be moved in the loading and ejecting directions jointly by an intermittent screw 105 which is not threaded in part near its drawing-in end, a support shaft 106 and a loading motor 107. A return spring 108 is arranged to aid the ascending/descending member 102 and the intermittent screw 105 for their screw engagement.
An opening-and-closing cover 109 is arranged to be opened and closed by an opening-and-closing motor 110. The opening-and-closing cover 109 is thus arranged to shield from light a cartridge chamber 111 which is arranged to accommodate the film cartridge 101. A film rewinding fork 112 is arranged to support the film cartridge 101 in conjunction with the opening-and-closing cover 109. The operations of these parts are controlled by a microcomputer 113.
An opening switch (SW1) 114 and a closing switch (SW2) 115 are arranged to detect the opening and closing of the opening-and-closing cover 109. An ejecting direction limit switch (SW3) 116 is arranged to detect the completion of an ejecting action of the ascending/descending member 102 on the film cartridge 101. A main switch (SW6) 119 is provided for opening and closing operations on the opening-and-closing cover 109.
The position (state) of the film cartridge 101 relative to the cartridge chamber 111 is detected by the combination of a loading drive start switch (SW1) 117 and a state detection switch (SW5) 118. More specifically, the microcomputer 113 determines the state (position) of the film cartridge 101 relative to the cartridge chamber 111 by the following combinations of states of the switches 117 (SW4) and 118 (SW5).
(SW4, SW5)=(off, off): a state in which the film cartridge has not yet been loaded or has been completely pulled out by the operator.
(SW4, SW5)=(off, on): a state in which the film cartridge is either in process of being pulled out by the operator or in process of being loaded. (SW4, SW5)=(on, on): a state in which the film cartridge is waiting for being pulled out by the operator after the completion of an automatic ejecting action, or a state in which an automatic loading drive is started after the completion of insertion by the operator.
(SW4, SW5)=(on, off): a state in which the film cartridge has been completely loaded.
However, the automatic loading and ejecting mechanisms arranged as described above have presented the following problems.
The switches for detecting whether or not the film cartridge has been inserted into the cartridge chamber by the operator to a position where the film cartridge has become able to be drawn in by the automatic loading mechanism are arranged to make such a detection by a side face 101-b of the film cartridge 101. In actuality, however, it is necessary to have some clearance between the film cartridge 101 and the cartridge chamber 111. The film-cartridge 101, therefore, might happen to irregularly move within a plane perpendicular to the loading direction inside the cartridge chamber 111. The irregular movement of the film cartridge 101 tends to incur inadequate contact of the switches which are of the contact type arranged to detect the side face 101-b of the film cartridge 101 as mentioned above. The automatic loading arrangement thus has the possibility of inadequate loading. Further, the arrangement using the engaging claw necessitates accurate detection of the inserted position of the film cartridge within the cartridge chamber in order to enable the engaging claw to engage with the film cartridge. However, unevenness in size among film cartridges tends to cause variations in timing of contact with the side face of the film cartridge. Under such a condition, the engaging claw might fail to engage with the film cartridge, thereby hindering adequate loading.